Method of making dry cells



Nov. 16, 1937. o. METZGER- METHOD OF MAKING DRY CELLS Filed Nov. 26,1934 0. j/[eiz Gttomeg Patented Nov. 16, 1937 UNITED STATES PATENTOFFICE METHOD OF MAKING DRY CELLS Germany Application November 26, 1934,Serial No. 754,805 In Germany November 14, 1931 4 Claims.

' This application is a continuation in part of applicant's copendingapplications Serial Nos. 600,753 filed March 23, 1933, and 659,021,filed February 28, 1933. 5 This invention relates to zinc containers forelectrical cells for dry batteries, pocket lamps, anode batteries andthe like and method of making same. Up to now such zinc containers havebeen made by bending a rectangular piece of zinc l0 sheet into acylindrical form, soldering its longitudinal edges together and thensoldering a circular end onto one end of the tube. Thezinc containersmade in this way, however, have the disadvantage that they are veryrapidly consumed by electrolytic actions. Zinc containers have also beenmade by a drawing process (that is containers drawn from a round disc).In this process however, the discs from which the containers are drawnhave to be greased. This 0 grease adhering to the container, which isvery disadvantageous for the electro-chemical use of the container, hasto be carefully removed by washing so that a further operation isrequired which makes the containers considerably more expensive.Moreover, the drawn containers have very sharp bottom corners which alsoare found to have a detrimental effect on the life of the container.

The present invention consists in this, that the zinc container is madefrom a small plate of rolled zinc by the known cold extrusion process.The zinc containers made by this method have the advantages over othercontainers of greatly increased life and completely smooth inner andouter surfaces. The containers according to the invention are furthercharacterized by the feature of being completely free from fat.

The so-called cold extrusion process for making tubes for pastes andsimilar cylindrical containers from aluminum, lead and tin is known butup to now it has not been proposed to use the cold extrusion process formaking zinc containers from rolled zinc plates (for example zinc discsof circular or other shape) which, on account of the great homogeneityof the initial material and its increase on account of this meth- 0d offorming and the considerable compression of the crystalline structure ofthe zinc which are obtained by impact, have their electrolyticproperties and their life improved to a very great extent and also havecompletely smooth inner and outer surfaces, which is very desirable. Itis known to make zinc containers by a hot extrusion process. Thisprocess is, however, expensive and does not give the very goodelectrolytic properties which are obtained in the present process. Themolecular structure of the zinc is altered with unsatisfactory resultsby the heating of the zinc.

Previous attempts in this direction have all 5 'given negative results.In particular, the industry concerned has not realized that rolled zincplates as a starting material, which is homogeneous in itself, show anunexpected improve ment of the electrolytic properties when extrud- 10ed in the cold.

Since the machines used for carrying out the cold extrusion process areknown, it will not be necessary to show these in a drawing in order tomake the invention clear.

In the accompanying drawing, Figs. 1 and 2 show the small rolled zincplate used as the initial material in plan and side elevation and Figs.3 and 4 show the zinc container made from this plate in partiallongitudinal section and in plan.

The zinc container (1 is made from a circular disc-like plate bconsisting of rolled zinc. This zinc plate has a diameter of about 18.5mm. and a thickness of about 5 mm. The zinc at ordinary room temperature(i. e. 15-20 C.) is subjected to the action of the extruding mechanismwhich in lieu of applying a steady pressure applies a sudden impact offrom 10,000 to 20,000 kg. per sq. cm, (142,000 to 284,000 lbs. per sq.inch). The plunger moves with a velocity of 150 mm. per second or more.

It is of course understood the extrusion of the zinc takes placebackwardly, i. e. in a direction opposite the movement of the plunger.

The zinc plate in the above-described cold extrusion process is shapedby a very sudden impact on the press to a cylinder with a bottom 0 whichhas about the same'diameter as the plate, has walls of uniform thicknessand is about 53 mm. high. i

The process is completed so speedily that the transforming process ofthe zinc is not visible with the naked eye. The zinc, however, shaped bythe said very sudden impact shows-in a further increase of thehomogeneous qualities of the starting material-an extraordinarily denseand homogeneous molecular structure, so that the zinc container made bythis method has excellent electrolytic qualities and therefore a greatlyincreased life. In addition a rounded bottom edge d is obtained and theinner and outer surfaces are smooth and mirror-like.

In amodiflcation of the above process, the zinc is preheated to a pointbelow 90 which latter is about the lower limit of recrystallization ofzinc.

In this modification as in the first form described, lubrication is notnecessary while the tools are not used up so rapidly.

What I claim is:

5 1. The cold, instantaneous, impact extrusion method of backwardlyforming an integral hollow zinc container with a closed end whichcomprises placing a disc-like plate of rolled zinc in a closed cavitywithout preheating said plate, impacting said zinc plate in said cavityat room temperature of about C. to about C. with one blow of a solidplunger almost filling said cavity and only leaving a. small openannular space, said impacting being efiected without a lubricant and in-15 stantaneously with an extremely high pressure of about 142,000 toabout 284,000 pounds per square inch whereby the extrusion of zinc iseffected in a direction opposite to the movement of the plunger sospeedily that it is not visible with the 20 naked eye and whereby anintegral hollow zinc container with a closed end and with smooth andmirror-like surfaces is formed with an extraordinarily dense andhomogeneous structure and with excellent electrolytic qualities andgreatly in- 29 crease life, and discontinuing the application ofpressureafter said one sudden impact blow has been effected momentarily.

2. The cold, instantaneous, impact extrusion method of backwardlyforming an integral hollow 30 zinc container with a closed end whichcomprises placing a disc-like plate of rolled zinc in a closed cavitywithout preheating said plate, subjecting said zinc plate at roomtemperature to an in- ,stantaneous impact with one sudden blow of aplunger moving with a velocity of at least mm.

per second, said sudden single impact blow being effected without alubricant and with an extremely high pressure of about 142,000 to about284,000

pounds per square inch whereby the extrusion of zinc is effected in adirection opposite to the movement of the plunger so speedily that it isnot visible with the naked eye and whereby an integral hollow zinccontainer with a closed end and with smooth and mirror-like surfaces isformed with an extraordinarily.dense and homogeneous structure and withexcellent electrolytic qualities and greatly increased life, andremoving said plunger from said formed hollow zinc conaoi tainer withoutthe application of pressure after said one sudden impact blow has beeneffected momentarily.

3. The cold, instantaneous, impact extrusion method of backwardlyforming an integral hollow zinc container with a closed end whichcomprises placing a disc-like plate of rolled zinc in a closed cavitywithout preheating said plate above the lower recrystallization limit ofzinc, subjecting said zinc plate below the temperature of the lowerrecrystallization limit of zinc to an instantaneous impact with onesuddenblow of a plunger moving with a velocity of at least 150 mm. persecond, said sudden single impact blow being effected without alubricant and with an extremelyhigh pressure of about 142,000 to about284,000 pounds per square inch whereby the extrusion of zinc is effectedin a direction opposite to the movement of the plunger so speedily thatit is not visible with, the naked eye and whereby an integral hollowzinc container with a closed end and with smooth and mirror-likesurfaces is formed with an extraordinarily dense and homogeneousstructure and with excellent electrolytic temperature of about 15 C. toabout 20 C. with 'one blow of a solid plunger almost filling saidcavity. and only leaving a small open annular space, said impactingbeing effected without a lubricant and instantaneously with an extremeiyhigh pressure of about 142,000 to about 284,000 pounds per square 'inchwhereby the extrusion of zinc is effected in a direction opposite to themovement of the plunger so speedily that it is not visible with thenaked eye and whereby an integral hollow zinc container with a closedend and with smooth and mirror-like surfaces is formed with anextraordinarily dense and homogeneous structure and with excellentelectrolytic quantities and greatly increased life.

- O'I'IO METZGER.

